1. Technical Field
The invention relates to the field of electronic circuitry testing, and more particularly to testing of revocable circuitry elements without the need of their removal from host equipment.
2. Background Art
Certain applications, such as the safe operation of nuclear power plants, rely on critical electronic systems to protect the plant, operating personnel and the public. To insure this equipment is operational, periodic testing is performed. The periodic testing may insure that the equipment is operational at the specific time of the test, but the equipment may be prone to undetected failure during periods between tests, which may reduce the safe or continued reliable operation of the nuclear plant, for instance. (Redundancy may be used to mitigate this risk.) Furthermore, many systems contain built-in functional test equipment that facilitates testing with the electronic circuitry boards installed in the equipment.
Since electronic equipment and its design may be under strict regulatory oversight, such as in the nuclear power generation industry, there is reluctance to replace equipment as it ages. Furthermore, the application of the equipment makes it undesirable from a safety aspect to remove a redundant set of equipment from service for other than the briefest period of time. To bring the entire plant to a shutdown condition to test the equipment more thoroughly is economically very undesirable. As electronic equipment ages, known degradation mechanisms may make the equipment more prone to failure, and the restrictions on removal from service for significant periods of time make it difficult to discover and diagnose these degradations.
To minimize the risk of equipment failing undetected due to aging, which may either compromise safety or compromise plant operations, some equipment owners remove electronic circuit boards from use in the host equipment and aggressively test them in test fixtures which examine them more closely than they can be examined in the system. This testing goes beyond the simple testing that is built into the host equipment.
However, this approach including circuit board removal may cause handling risks to the boards and requires extended durations of down-time to complete.
While built-in test circuits are not uncommon in many critical applications, built in test circuits that can predict an impending failure, especially without applying additional stress to the circuit, are believed to be unknown. Thus the major feature of the present invention is the ability to do detailed analysis on the performance of the circuitry under test to determine if the circuit's electronics are aging (i.e. deteriorating over time) without having to remove the circuit card from its environment.
Since removal and handling and testing in foreign apparatus is understood to be a risk for a critical circuit, in a nuclear power plant, where aging electronics are the norm, the ability to identify deterioration due to aging mechanisms without increasing the risk that these aging, and hence more fragile circuit cards, will actually fail is of great financial interest to the system owner/operator. A seemingly random failure of a circuit can cause a power plant to shut down. Unanticipated shutdowns take hours if not days to diagnose, understand, investigate and document before the plant can be restored to generating electricity. Lost revenue for each day the plant is not operating may be in the order of $1M.
While the above cited references introduce and disclose a number of noteworthy advances and technological improvements within the art, none completely fulfills the specific objectives achieved by this invention.